Changes in FiDeL parameters, pending issues and cross-checks for LHC 2012

1. Changes in FiDeL parameters,pending issues and cross-checks for LHC 2012 Per Hagen (TE/MSC) FiDeL Team26.03.2012

2. Changes in FiDeL parameters for 2012 • Correction of some harmonics per circuit • MQXB b6 circuit values were random junk (probably a wrong Excel copy & paste) • MQXB2.R1 .R2 .R5 a4, b3, b5 wrongly rotated (due to a false assumption in Excel sheet) • Guilty: Per • Discovered when fine-checking circuit versus magnets(in the context of the triplet correction for 2012 final squeeze)

3. Changes in FiDeL parameters for 2012 • Reducing number of fitting constants to match what LSA can cope with (per circuit) • MBX b3: DCMAG mu now expressed at 300A, like TF • MBX b5: DCMAG mu and RESMAG rho now expressed at 300A • GM_MQXB b6 : DCMAG-I_inj_ref for b6 equal to TF. Rescaled DCMAG-mu to match TF. Changed Ic to match TF (no rescaling possible)

4. Pending issues in FiDeL parameters! • Massimo Giovannozzi draw my attention to some strange old inconsistency between harmonics for triplets which exists since the first FiDeL parameter set • Discovered when comparing old WISE “collision” data (using “high-field” data extracted from database) with current FiDeL data • Some MQXA harmonics appear rotated: B'(odd) = -B(odd), A'(odd) = -A(odd) for Q3 in tunnel (not all!) • Compatible with “upside-down” rotation • Q1.L8 very different all harmonics • Q1.R2 b6 different • I never thought of making a cross-check between old WISE data and FiDeL Inconvenient Truth

5. LSA cross-checks for 2012 • LSA beam processes checked • PRECYCLE_4TeV_V1 • RAMP_4TeV_2012_V1 • RAMP_4TeV_MCS_2012_V1 • SQUEEZE_4TeV_2012_V1 • RAMPDOWN_4TeV_V1 • What has been checked • “P2N” : Power Converter limits not exceeded • “P2R” : Pre-cycle versus ramp cycle in “harmony” • “An/Bn”: Subset of FiDeL multipoles used in LSA beam processes • “K” : Optics strengths agree with optics files; constant or F(beta*) • “I” : FiDeL circuit currents agree with K-values • What has NOT been checked • MB b3 and b5 decay during injection (no LSA data) • Arc correctors which strengths are entirely managed by LSA (depends upon optics algorithm not in WISE) • Chromaticity correction during squeeze (sextupole strengths not published in optics squeeze files) • Strengths of optics incorporated in LSA from run-time (orbit & bumps, octupoles)

6. Results from LSA cross-checks for 2012 • Hard to find issues (wasted time?!) • Pre-cycle • As usual wrong I_MIN in P2N for RD34.LR3. 40A instead of 18A. ACC_SETTINGS_DB does not reflect reality! • Pre-cycle versus ramp (pre-cycle = pre-cycle or ramp-down after physics) • These circuits should have max current increased in pre-cycle to match ramp-down: MQXA, MQXB, RCD, RQF, RQD • RCS should have max current increased in ramp-down to match pre-cycle • These circuits should have max current increased in both pre-cycle and ramp-down to match max current: RD1 cold, RD2 cold, RD3 cold, RD4 cold, probably RMSD, RQ5.L6, RQ5.R6, RQ6.L3, RQ6.L7, RQ6.R3, RQ6.R7

7. Results from LSA cross-checks for 2012 • Squeeze • RCB K never correspond to official squeeze optics • Some matched optics points not used (just an observation) • Ramp • RCD.A78B1, RCDA78B2 : IMAX exceeded by a few mA • RCBXH1.L1 has only a positive cycle. Expect + and - cycles as for 2011 • Wrong sign found for current in RCBXH3.L8 (polarity wrong in power converter or wiring)

8. MB b3 / b5 correction • Changes in powering history (2012 versus 2011): • Flat-top current increased: 6000 A -> 6740 A • But as we agreed on disabling FiDeL MB b3 energy scaling of amplitude in 2011: MB b3 snapback unchanged • MB b5 • 10% different from WISE during first 30 seconds (see next slide) • after that perfect agreement • WISE has currently MB b5 energy scaling of amplitude disabled (as for MB b3). Right or wrong?

10. Ongoing cross-check activity • Correction of IP optics using triplet correctors • Errors in triplets and D1 important when IPs -> fully squeezed • Depends upon optics algorithm not in WISE (LHC project note 349) so do it from scratch • Reference implementation in Fortran by SF • Limited success yet for myself (I used thick lens instead of thin lens) and the algorithm is very sensitive to changes in betatron functions • In this context the question about inconsistent values for triplet harmonics, old WISE versus FiDeL has been raised (mentioned earlier in presentation)